Optical discs are often contained in protective cartridges or boxes; however, the cost and bulk of changers for optical discs in cartridges or boxes is such that their use is limited to the professional field. To popularize the use of optical disc changers in the consumer market, it is essential to reduce their cost to the consumer, which means that the discs must be stored in the changer as they are, i.e. without individual protective cartridges.
Many mechanisms for transferring discs or cassettes have been proposed in the past, but these are either bulky or complex or lack the requisite precision, or need an additional mechanism to release the edge of the disc to allow the disc to rotate freely when it is in the operative position.
U.S. Pat. No. 4,750,160 discloses a transfer mechanism which grasps discs to guide their translation and utilizes a lateral movement of the disc into a wider housing provided in the transfer mechanism to allow the disc to rotate freely in the operative position. Such a system requires high precision for the various components, particularly those effecting the return of the disc into a narrow receptacle after playback.
Moreover, any flaw on the edge of the disc or rolling surfaces can set the disc askew and either damage its surface by contact with the walls or cause it to jam.
Finally, it is clear that this transfer system allows the discs to be maintained only approximately in the storage position since the two guiding and holding points have to be very close.
British published Application 2161013A discloses a transfer mechanism which utilizes a sliding transfer member having a pair of guide arms, the gap between the two arms being sufficient to allow the disc to turn freely in the operative position, thereby avoiding the need for a wider housing and lateral movement of the disc to the operative portion.
However, such a system provides only very imprecise guidance of the disc and can only be used with a magazine holding the discs approximately--the two holding points are also very close--and requires partition walls, which add to the cost of the magazine, which reduce the number of discs the unit can contain, and which can cause damage to the surfaces of a disc when the disc is being transferred. A similar system, having the same kind of drawbacks, is proposed in German publication DE-OS 1161052.